1. Field of the Invention
The present invention relates to a belt type continuously variable transmission and an engine including a belt type continuously variable transmission.
2. Description of Related Art
A belt type continuously variable transmission includes a primary sheave and a secondary sheave, each having a groove with a variable width. The primary sheave is mounted on a primary shaft to which an output from a power source such as an engine is input, and the secondary sheave is mounted on a secondary shaft from which an output for a driving wheel is output. The primary and secondary sheaves are each made up of a fixed flange and a movable flange defining a V-groove therebetween. Each movable flange movable in an axial direction of the primary or secondary shaft. A V-belt is wound around both sheaves. The gear ratio of the belt type continuously variable transmission is varied by moving the movable flange to vary the groove widths of both the sheaves.
Some V-belt type continuously variable transmissions include a control device for controlling an actuator for moving the movable flange of the primary sheave. The control device calculates a target gear ratio based on vehicle information such as throttle opening degree and vehicle speed, for example. In order to move the movable Range to a target position, the control device sends a control signal to the actuator to control the position of the movable flange. Such V-belt type automatic continuously variable transmissions are applied, for example, to vehicles such as motorcycles (see JP-B-3043061, for example).
The continuously variable transmissions in JP-A-Hei 7-158706 include a position sensor for detecting the position of the movable flange. JP-A-Hei 7-158706 discloses that factors such as variations in output characteristics of the position sensor, changes over time in the characteristics, and elongation and wear of the V-belt impair the consistency of the correlation between the value detected by the position sensor and the position of the movable flange. JP-A-Hei 7-158706 further discloses self-correction of data of the impaired consistency of the correlation based on the ratio between the speeds of the primary and secondary sheaves.
The continuously variable transmission of JP-A-Hei 7-158706 is subject to the influence of dimensional tolerances of the mechanism, variations that occur during the assembly, and so forth, because of the construction that the position of the flange is detected by the sensor. Therefore, the control device needs to be adjusted so as to be able to correctly control the flange based on the detection value of the sensor after assembly of the sensor and the mechanism for moving the flange. Such adjustment needs to be made for each vehicle and after each maintenance such as replacement of the belt. Therefore, the adjustment is desirably made in a simpler way.